The filter we designed works for the most part. However, there are a few problems. Because the Waldo images are each hand-drawn, it can be difficult to match the Waldo head template with the image in question. For example, in this image,
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This type of mistake occurs when the template image does not highly correlate with the reference image. These errors could be corrected if a database of Waldo's were created and each one referenced instead of just having one Waldo template image.